


Assimilation

by WildWhim



Category: Original Work
Genre: Alternate History, Body Horror, Childhood Friends, Demons, Gen, Gender or Sex Swap, Hive Mind, Japanese Character(s), Long Hair, Male Friendship, POV First Person, POV Third Person, Swearing, Tails, Teenagers, Weird Biology, What is a man?, you are what you eat
Language: English
Status: In-Progress
Published: 2019-03-26
Updated: 2019-03-26
Packaged: 2019-12-18 04:30:01
Rating: Teen And Up Audiences
Warnings: Graphic Depictions Of Violence
Chapters: 2
Words: 3,529
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18242411
Author URL: https://archiveofourown.org/users/WildWhim/pseuds/WildWhim
Summary: At the request of his friend, Sion Inada enters an abandoned mansion, which is surprisingly well preserved despite the terrible events of a past war. Unfortunately for him, the building is not as empty as he thought it was and he ends up losing his humanity due to his own carelessness...although he does look like a rather cute girl now. While he and his friends are trying to figure out how a being composed of hundreds of confusing and unpleasant creatures is supposed to live, the long forgotten enemies of mankind are preparing for an attack.





	1. One missed detail

**Author's Note:**

> I have always been interested in stories in which one of the main characters turns into something inhuman and eventually adapts to all changes. There are vampires, werewolves, demons, etc., but those are rarely different enough from humans as far as biology and such goes. I am also interested in creatures with unusual physiology. After adding a couple other things to the mix, I got this idea.
> 
> I have 6 chapters written at the moment. While writing the last one, I drew a rough sketch (or whatever should be the term) of the main character in his state at the end of the 5th chapter: https://i.imgur.com/lltn5Wi.png It's a very minor spoiler since his general appearance doesn't change much there from the second chapter aside from a few things.

Once again, Sion considers quitting.

If it weren't for Yukiko, he would have never even come close to this old mansion. Of course he is aware that the building is special. When exactly it was build is unknown, but it's been here before the war broke out and it somehow survived while every other building near it were completely destroyed. Anyone who has never heard of it would have taken it for something brand new. There aren't even any cracks on it.

But that girl isn't interested in it because of its history. There is something wrong with it. Simply looking at it is unpleasant and everyone avoids coming close. There are quite a lot of rumors about this building. Many think that it's haunted by ghosts and that all sorts of rituals not to be described have taken place there. Yukiko has always been interested in this sort of stuff and this mansion has long caught her eye, but she has no time to inspect it closely herself.

Unfortunately for Sion, he had more than enough free time and so he couldn't refuse her. They have long been acquainted and so she approached him first. All he had to do was to take a photo of whatever he deemed interesting and pass the results to her. There was nothing difficult about it even if he had to do it late at night.  
  
And yet he is scared...just a little. Of course, it has nothing to do with the scary stories he heard, but rather the age of this building. Although it might look stable on the outside, he has no idea what it's like inside. It could collapse at any moment and Sion doesn't want to be inside when that happens. On the other hand, it's been here for a very long time and it somehow lived through the war, unlike a good majority of Japan. This isn't exactly a matchstick house and he's well aware of it, but that premonition of imminent disaster doesn't leave him.

  
Having gathered his bearings and taken a deep breath, the young man ascends the steps and carefully opens the front door. For some reasons, it's not locked and so he has no need to use a crowbar, which pleases him as he did not want to break it at all. It turns out to be quite dark inside and he pulls out a flashlight out of his backpack to take care of that issue although the quality of the pictures will suffer from it. To his surprise, everything is just as well preserved on the inside as it is on the outside. The floor doesn't even creak. It's obvious that a lot of money was spent on the building.

Having seen nothing interesting at the entrance, Sion moves on. The doors on the second floor turn out to be locked and so he decides to explore the first floor, but before going back downstairs, something on the wall draws his attention. Upon shining the flashlight on it, he sees a rather large portrait. Its top half is completely missing as if somebody tore it in half, but judging by the hands folded on the depicted person's knees, it's a woman in her thirties. Once he takes a photo of it, Sion keeps going deeper.

With every step, the feeling of fear only grows stronger, but he simply has to keep his word. He has no reason to fear anything and as such, he has no reason to stop. It's just an old mansion which some incredibly skilled architect has been commissioned to build by some very rich man. And yet something about this place seems...unnatural and empty. It gives the impression that nobody has ever lived here and the building itself had an entirely different purpose. All furniture is in perfect condition and it's obvious that nobody has ever touched any of it. Everything looks like a very beautiful painting rather than a house. Only the portrait was an exception to this and this raises some red flags along with the lack of locked doors.

Unfortunately, he doesn't get to explore all the room before he falls through the floor with a scream. So the building wasn't as well preserved as he thought. Fortunately, he didn't break anything, but he did cut his hand while trying to grab onto something and the wound is quite deep. He should leave this place as soon as possible, but first, he needs to find a way back up. Having found a door in front of and several feet behind him, Sion decides to enter the one that's closer to him.

Taking a look around, the young man finds something that is sure to please Yukiko. He doesn't know where he found himself, but all the walls and even the ceiling are covered with odd hieroglyphs. How and with what those were written is not something he wants to know. He's more concerned about his hand and almost forgets why he's here. He also recalls all that nonsense about the rituals. Perhaps those rumors weren't so unfounded after all and the mansion's former owner actually had some quirks. Then again, it's hard to explain the state of the building otherwise.

In addition to the inscriptions, Sion finds shelves with many glass containers. Most of them are empty while the contents of most of the still sealed ones are hard to discern. The young man takes one of them and tries to figure out what sort of creature is within it. A rather large black body with two pairs of segmented limbs brings insects to mind, but the long tail and jaws full of sharp teeth confuse him and he tries to read the label. It's written in English and Sion needs a bit of time to remember everything he has learned.

"Scyl...lla...Scylla?"

The next few rooms turn out to be in the same condition while the last one differs greatly. It's much larger than the previous ones and something's inscribed on the floor, but the young man's attention is drawn by something in the middle of it. He doesn't even need a flashlight to recognize a human body. Sion immediately runs up to the woman lying on the floor and tries to wake her up...but then he notices her wide open eyes and almost drops her onto the floor out of fright. She's already dead, but there are no visible wounds on her body or even bloodstains. The knife held in her hand is also clean.

What is she doing here? How long has she been here? What happened? These questions remain unanswered. Taking a closer look at the corpse, Sion recalls that torn portrait, but it couldn't have been that woman as this mansion has been abandoned for a very long time. Even if she has lived here at some point, her body would have gone through at least some changes. This person must have died recently.

Perhaps the young man shouldn't forget about his wound. While he's asking himself unnecessary questions about the nature of this mansion, blood slowly trickles down his arm and ends up dropping on the circle drawn on the floor.

Bright red light temporarily blinds Sion and then an awfully loud noise rings out. All glass containers around the young man immediately shatter into thousand shards. Fortunately, they are too far away from him to harm him, but it's too early to rejoice. Everything that has once been sealed inside is now free and already advancing towards Sion. One of these things decides to jump at him and easily pins it to the floor. He manages to grab it and throw it off himself before it can maul him, but many more of these things follow it and he has to run.

Trying to close the door behind him to slow down these monsters only wastes precious time and energy. It takes no effort for them to chew through the door and one hole is enough for the rest to squeeze through. It would be much easier for him to run if he was more used to it, but they turn out to be a little slower and this mansion can't be big enough for him to run out of stamina before he can find an exit out of this cursed building. And yet Sion has to throw off his back some of these black critters a few times. A shower after this is all over won't hurt.

But these thoughts are best left for later. The young man finds a locked door blocking his way at the wrong time. A crowbar is needed and he needs to work fast. He has no time to use it correctly and so Sion starts to simply beat the door with it. It's not very durable and he runs upstairs. Fortunately for him, the black mass has a hard time climbing the stairs and the distance between them grows.

Having returned to the more familiar hall of the first floor, the young man heads towards the entrance. He doesn't let his guard down even when he finally leaves the mansion and runs to his house, stopping only when he reaches the front door. His legs ache, he's breathing heavily and his hand is still bleeding, but this doesn't matter anymore. Closing the door behind him, Sion tosses his backpack aside and goes to the bathroom, undressing on the way there. He simply has to wash away all this slime as soon as possible.

He knew that it wasn't such a good idea, but everything turned out to be much worse and he'll never enter that mansion even if that ends up upsetting Yukiko. Neither she nor anyone else for that mater should ever come close to it. It must be burned and forgotten about. Why would anyone keep such creatures? What happened there anyway? And once again, there are more questions than answers. He was supposed to relax today. Maybe it would be better not to think of it. Just take it easy.

Exhausted, terrified and a little hungry, the young man goes to the bedroom and falls onto his bed with relief, almost immediately falling asleep.

Something inside his backpack starts moving and in a few seconds easily slithers out of it. Two pairs of limbs drag a long tail behind them, leaving a trail of slime. This thing doesn't have much time left, but it's enough. The smell of a human is hard to miss and this creature quickly finds him, silently climbing onto the bed. It takes no effort for it to find his ear and, shrinking itself to the right size, it crawls inside.

Sion doesn't even notice how something begins to eat him from inside out...but that's not the worst thing that will happen to him. 


	2. Stranger

Phew, I've made it. I'll never go there again. Just ended up wasting time.

One turn clockwise and the door opens. I w-

I almost trip over a backpack lying on the floor. What is it even doing here...and the hell's this shit? Doesn't seem to smell, but it looks disgusting. I don't even know what to compare it with...well, aside from...

After giving the dirty backpack a good kick, I go to the bedroom to change out of these clothes. I'm wearing a shirt and a tie and the heat still got me when it's long been autumn. I would have taken this formal leash off, but we can't do that. I say it's bullshit. It's not like coming to an interview in nothing but underwear. Wearing a dress shirt isn't a problem, but this...

Somebody's sleeping on Sion's bed...Ohoho, our boy is all grown up now! He has already brought a girl into our house and he didn't even call me up! I feel a little bitter, but I'm too proud of him to dwell on it. And here was I, thinking that he loved Yukiko and I've long been ready to talk him out of it. Nothing wrong with her appearance, but she's really weird. She likes all that crap with ghosts, demons and...the occult? That's what it's called? Either way, not somebody he should be spending time with. But if he's with somebody else, then I can relax.

Well, the girl looks quite good from what I can see, which is only her head and almost all of her black hair since the rest remains under a blanket. Straight fringe, knee-length sidelocks and...It's hard for me to tell how long the rest is. It's gotta be dragging along the ground all the time. On the one hand, not everyone can grow their hair to that length, but on the other hand, that's gotta be inconvenient.

...Maybe I shouldn't keep staring at a sleeping person...although she does look rather cute like this. However, there's something wrong with her skin. Can't tell whether it's makeup or not, but it looks snow-white.

And where is our lucky man? He usually sleeps until dinner, but he's not here. Trying to find him in other rooms proves fruitless. Where did he go? Moreover, leaving a girl alone at home is wrong and it's not like him to do such a thing. Maybe she knows where he is...but then I'll have to wake her up...Awkward. If I'm left with no choice, then I might as well try to do is as gently as possible. And while I'm at it, I'll find out whether she is the right girl for him or a bitch I've gotta kick out.

At first, I gently nudge her shoulder. The girl is really small compared to me and so it ends up being not as gentle as I'd like, but it's still not enough. I've learned how to wake Sion up a long time ago, but I don't think I can just tear the blanket off her.

"Hey...wake up..."

This doesn't work either. She simply retreats deeper under the blanket. Birds of a feather...There's only one option left. I pull my phone out of my pocket and configure the alarm clock to ring out in a minute. It's usually loud enough to wake everyone up. It pisses me off, but I can't do without it. I used to have no need for such thing, but it got hard to wake up when needed as time passed.

The alarm clock rings out. Just as I expected, her arm emerges from beneath the blanket to turn it off and then the rest of her follows...She's wearing his clothes? Looks like our man isn't as timid as he seems. Of course, the pajama are too big for her, but that makes it even better. It's a shame she's already taken.

"Well, sleeping beauty, where's the prince?" - I ask.

"Lemme sleep...It's sunday..." - she replies, sleepily rubbing her eyes. Now I notice that her hair is crimson on the inside. I have no idea how you can even die it like that, but I'm not really interested in that kind of stuff.

"I'm aware of that, but where is Sion? He couldn't have run away, right?" - I ask. For some reasons, that pisses her off.

"I'm in no mood for your jokes, Jin", - the girl says. Something bothers her and she tries to clear her throat out for some reasons. I don't think there's anything with her voice...Hm...She already knows my name. Looks like he told her about me.

"Relax, I'm just looking for my friend. I can't find him anywhere", - I try to tell her. Finally, she stops rubbing her eyes and now I see that they are red. Can you even sleep with contacts?

"I'm right here. Satisfi-"

Suddenly, the stranger freezes. She grabs one of her sidelocks with wide open eyes, then lowers her gaze and...starts patting herself all over as if she's got spiders under her skin and she's desperately trying to find them. While I try to figure out what the matter is, she runs into the bathroom, almost tripping over her own hair. And here was I, thinking that Yukiko was weird. This isn't much bett-

I run after the girl as soon as I hear her scream coming from the bathroom and then a bang. When I enter the room, I see her on the floor in front of a mirror. She backs away from it with a frightened expression on her face until her back touches the wall. I don't even know what to say. What the actual hell is going on? I just can't wrap my head around it. Everything was fine at first, but now...What is she afraid of?

"Is something wrong?" - I ask and the girl immediately turns her head towards me.

"Jin! I-It's me, Sion!" - she says.

"...what?"

"I-I-I don't know what's going on, but it's really me!" - the stranger repeats.

Now I'm totally confused. It doesn't seem like a stupid joke. She's genuinely scared. But then why would she say something so stupid?

The more I think about it, the more I start doubting my own conclusions. Sion is still studying and, as far as I know, he had nothing planned for the weekend, and when he's got nothing to do, he sleeps all day. Besides, hooking up with girls is just not something he does. He's so indecisive and he still hasn't even confessed to Yukiko. Even if he had some relationship with someone, he certainly wouldn't leave her alone here. And, of course, he would have told me about it. We're not exactly strangers as we know each other since we were children.

Well, I've gotta do something with this psycho. Simply kicking her out isn't such a great idea. There's no knowing what kind of shit she'll pull out there. First of all, I've gotta calm her down. Whatever she thinks is the truth, it would be easier to deal with her once she's completely calmed down.

"Just breathe...or whatever people say in this sort of situation...Uh, just take it easy, everything's okay", - I say, making sure to keep a distance between us.

"Y...You're not...How can I convince you...Jin! Ask me a question that only Sion can answer!" - the stranger almost shouts...Maybe that will help her?

"Hm...I don't know what to ask..."

"Taking ages to think it through as usual...Got it! Remember Masumi? Masumi Takami? You had a crush on her and wanted to invite her to a dinner, but then I told you that she's actually a guy. Only one man knows about it", - she says...Sion certainly wouldn't have told anyone about it...But then...

I don't even bother holding back laughter. I lose track of time and it takes me a while to stop laughing my ass off. Such reaction doesn't please her- I mean him, but you can't blame a dog for barking. And when I start getting over it, I see his expression and it beings anew. It's getting hard to breathe, but dying from laughter isn't a bad way to go.

"And how did this happen?" - I try to ask while I still can.

"I've told you that I don't know! Sometimes, you're unbearable..." - he replies, crossing his arms over his chest...Speaking of which, that's not a bad pair at all. Yukiko will certainly envy him...that is, if she even cares about it.

"Well, at least you look pretty...This isn't contagious, is it?" - I ask and this certainly pisses him off. He finally stands up and approaches me...and it gets hard for me not to laugh. He's barely a meter and a half tall.

"Shut up! Do you even understand what sort of trouble I'm in? I can't go to school like this and all the documents...I'm screwed! People don't just change their appearance so suddenly and especially not to this extent! What am I even supposed to tell my parents? I can't even imagi-"

A strange noise immediately silences him. I loo-

"Sion, your arm!"

He doesn't understand what's wrong at first, but as soon as he lowers his gaze and sees his arm lying on the floor, he screams his head off. What the actual fuck is going on?!...It's still moving? And I'm pretty sure fingers don't bend that way! When that limb starts to break up into some black shit, I'm the one who starts screaming. I'm not exactly a coward, but I was never fond of slimy crawling things and this whole situation makes it even worse!

"They again?!" - Sion shouts, trying to get away from these creatures.

"Again? You've seen them before? What is this?" - I ask.

But before he can reply, these things leap at him and...disappear? Where did they...His arm...At first, that black mass emerges from his sleeve and then changes colors and shape until it finally assumes the form of a slender feminine hand as if nothing happened.

For a while, we just exchange glances and try to understand what the fuck just happened.


End file.
